Adjustable tuning device and antenna using same



May 2, 1961 R. H. BRESK ET AL 2,982,964

ADJUSTABLE TUNING DEVICE AND ANTENNA USING SAME 1I i e Inventors.

ADJUSTABLE TUNING DEVICE AND ANTENNA USING SAME Filed March 26, 1957 May 2, 1961 R. H. BREsK ET AL 4 Sheets-Sheet 2 .K m 5 6 0 A n M5 0 W O RA M v. i B 1 M n m cm l?! May 2, 1961 R. H. BRESK ET AL ADJUSTABLE TUNING DEVICE AND ANTENNA USING SAME 4 Sheets-Sheet 5 Filed March 26, 1957 May z, 1961 VAR/A805 FORCE R. H. BRESK ETAL ADJUSTABLE TUNING DEVICE AND ANTENNA USING SANT:

Filed March 26, 1957 4 Sheets-Sheet 4 Unted States Patent O 2,982,964 ADJUSTABLE TUNING DEVICE AND ANTENNA a USING SAME Raymond H. Bresk, Clifton, and Charles P. Majkrzak, Nutley, NJ., assignors to International Telephone & Telegraph Corporation, Nutley, NJ., a corporation of Maryland Filed Mar. 26, 1957, Ser. No. 648,564 Claims. (Cl. 343-895) This invention relates `to tuning devices, and more especially it relates to devices for adjusting the inductance and capacitance of a resonant electric circuit. f

A principal object of the invention is to provide a novel, simple and readily adjustable tuning devicey of the axially extensible and retractable kind.

Another object is to provide a novel adjustable inductance of the coiled spring kind.

A further object is to provide a novel antenna tuning inductance.

A feature of the invention relates to an adjustable tuning inductance in the form of a multi-turn helical spring having successive turns of dilferent diameters whereby a predetermined variation of inductance can be effected over a selected tuning range by compression or decompression ofthe spring.

Another feature relates to an adjustable tuning inductance in the form of an axially compressible and eX- tensible tapered multi-turn helical spring. v

A further feature relates to an improved tuning inductance comprising a multi-turn helical spring of nonuniform turn diameter, in conjunction with a novel adjusting and turn stabilizing arrangement.

A still further feature relates to the novel organization, configuration and proportioning of parts which cooperate to provide a simple and readily adjustable antenna tuning inductance.

Other features and advantages will appear from the ensuing descriptions, the appended claims and the attached drawing.

In the drawing, which shows by way of example certain preferred forms of the invention,

Fig. l is a diagrammatic view of an antenna embodying an adjustable tuning element according to the invention;

Fig. 2 is a View similar to Fig. 1 showing a different adjustment of the tuning element;

Fig. 2A is a View similar to Fig. 1 showing the supporting sleeve as part of the antenna radiator;

Fig. 3 is a detailed diagram used in explaining the inn vention;

Figs. 4 to l1 are further explanatory diagrams;

Fig. l2 is a sectional `view of a modiiication of Fig. l;

Fig. 13 is a magnified view of a further modification of Fig. 1;

Fig. 14 is a modification of Fig. 13;

Figs. l5 and 16 are detailed diagrams of a further modification of the invention;

Figs. 17 and 18 are diagrams of an additional modilication of the invention;

Fig. 19 is a diagram of a still further modification of the-invention; y

Fig. 20 is a series of graphs explanatory of the invention.

Referring to Fig. l, the invention is shown as embodied in a tunable antenna structure. That structure may comprise a conductive plate 10 which constitutes the wellknown ground plane of the antenna. The plate 10 has an opening which communicates with a coaxial transmission line comprising, for example, the center rod con- Patented May 2, 1961 firice ductor 11 and the spaced cylindrical sleeve conductor l2,

Vthe latter being fastened in any suitable manner tothe rod 11 may be connected to any suitablev operating mem- Aber to raiseand lower the rod with 'respect to the ground j 'y plate 10 The lowermost turn 15 of spring 1'4 can be welded or otherwise anchored to the upper face of plate 10. Merely as an illustration, thevcenter rod 11 may be threaded at its lower end and engaged by a corresponding threaded metal sleeve 16, the turning of which causes the rod 11 to be raised or lowered.

It is clear, therefore, that by raising and lowering the -rod 11, the axial length of the spring4 unit 14 can be correspondingly changed.- This adjustment, in effect, changes the physical length of the antenna above the ground plane, and as will be explained hereinbelow, it also changes the inherent inductance and inter-turn ca.- pacitance which, therefore, also provides adjustment of the electrical resonance of the antenna. It will be understood that the line 11-12 may be either a longitudinally rigid unit, or it may take the form of a whip antenna such as is used on automobiles yand the like.

Fig. 1 shows the antenna unit 14 in an intermediate compressed setting wherein the rod 11 has been `drawn down so as to effect a contacting compression of only the lower three turns 15, 17, 18. Since those turns vare effectively short-circuited to each other and to the ground plate 1, they are in effect inactive as separate inductance turns. On the other hand, the remaining non-contacting compressed turns constitute an electrically active multiturn inductance coil. Fig. 2 shows that by moving the rod 11'inV even a lower direction, the'ratio of the active to inactive turns of unit 14 can be greatly changed, thus adjacent active turns for any adjustment occurs at those a regions along the axial length of the unit where the higher voltage conditions occur. diagrammatically. in Fig. 3.

In Fig. 2A, the antenna radiator is shown to include spring 14a and also the sleeve 12a which supports plate 19a in coupled relation to the lower end of the spring 14a. f The sleeve 14a is supported by an insulating base 12b whichhouses mechanism 16a for raising and lowering rod 11a which is connected to the upper end of the spring 14a. The antenna coupling is at the base of the sleeve 12a as indicated at 12e. By adjusting the position of the rod 11a the radiator length h may be varied and tuned simultaneously.

Referring to Figs. 4 and S, there is illustrated in more detail the manner in which the spacing between the suc- Vcessive turns of the tapered helical spring Varies. Fig. 4 shows the unit 14 in its completely axially relaxed state. Preferably, `although not necessarily, the spring is formed with the normal relaxed turn spacing S equal to the That relation is shown The axial actuating force on the spring thus causes the turns of larger diameter to deflect at a greater rate than the smaller diameter turns. The reason for that is, in loading or axially compressing any multi-turn helical spring, each turn may be considered as the equivalent of a long cylinder which is subjected to torsion; i.e. twisting by terminal couples. The deflection of each turn is proportional to the degree of twist in its equivalent cylinder. In the case of a non-tapered spring, as shown in Fig. 6, each turn being cylinders of equal lengths, is subjected to the same amount of twist by the load F, and

therefore the turns deflect uniformly. Fig. 7 illustrates N the equivalent cylinders of equal lengths, Cm, and Fig.

an axial compression, each turn, having a different mean diameter, and therefore equivalent cylinders of unequal lengths, each turn is subjected to a different torsional twist by load F. Since the deection of each turn is proportional to the degree of twist of its equivalent cylinder, each turn will deiiect at a different rate.

Fig. 10 illustrates the equivalent cylinders of unequal lengths, Cm, and Fig. 11 illustrates the dilerence in the torsional twists found in them. Each turn will therefore deflect a different amount from the other turns, but the deflection of each turn will be proportional to a given load on the spring.

Fig. 12 shows how the invention may be employed in a tuning unit for any conventional kind of antenna which is schematically represented by the numeral` 19. The antenna tuning unit 14 comprises a tapered helical spring such as disclosed in Figs. 1 and 4 and housed within a closed metal housing or box 20. Slidably passing through the lower end of box is a rod 21 which carries at its upper end a iiat metal plate 22. Plate 2-2 is lprovided at its periphery with a `plurality of flexible arms 23, 24 which bear against the inner wall of box 20 to make electrical contact therewith and to maintain the unit 14 central within the box while permitting the plate 22 to be moved towards and away from the bottom of the box. For that purpose the rod 21 can have any suitable operating member represented by the gear wheel 25 which may be in engagement with the threaded end 26 of rod 21. Insulatingly fastened through the upper end of box 20 is a rigid lead-in 27 to which the top turn 28 of the tuning unit 14 is anchored. The lowermost turn 29 can be suitably anchored to plate 24. Therefore as the rod 21 is moved it changes the number of eiective spaced turns of the unit 14 with respect to the compacted contacting turns of that unit, thus changing the inductance of the unit 14.

Referring to Fig. 13, there is shown a modification of the device of Fig. l2. It comprises a metal housing 30 having a tubular extension 31 in which is slidable a coil form 32 of insulation. Form 32 is attached to a metal plate 33 carried by rod 34 and provided with a suitable operating means for moving the rod in the direction of the arrows. The insulator form 32 is of tapered shape and is provided at its upper end with a peripheral notch in which is seated the topmost turn 35 of the coiled helical spring 14 which may be of the same construction as the corresponding springs hereinabove described. The lowermost turn 37 rests against the ange portion 38 which forms a shoulder with the inner edge of the corresponding ilange 39. If desired, the turn 37 can be welded or anchored to the flange 38.

In its fully relaxed state the spring 14 urges the member 32 upwardly so that all the turns of the spring are out of contact. If desired, a suitable stop may be provided to limit the upward movement of member 32 to permit the spring to assume its fully relaxed condition representing the maximum inductance setting of the device. To decrease the inductance the rod 34 is moved downwardly to compress the larger diameter spring turns as hereinabove described. The topmost turn 35 can be connected by a suitable wire 40 to any suitable antenna 19. The taper of member 32 is designed so that when the member is in its uppermost setting it matches the taper of spring 14 when the latter is in its fully relaxed condition.

In order to dampen the spring turns against vibratory shock or the like, the outer periphery of member 32 has a continuous helical shoulder having the same number of Y convolutions as the number of spring turns. Therefore the non-contacting turns of the adjusted spring are retained by their inherent springiness against the shouldered groove of member 312, thus supporting them against vibration. The contacting turns 41, even though they become of larger diameter thenthe corresponding region of member 32, do not require any additional support against vibration because of their compacted condition.

Fig. 14 shows a modiiication of Fig. 13 wherein the spring 14 is supported against vibration by an insulation l coil form 42 which, however, is stationary. The form 42 is fastened to a metal plate 43 held between the two parts 44, 45 of the enclosing metal box. Plate 43 has a pair of diametrically opposite guiding bosses 46, 47 through which pass the upright arms 48, 49 of a U- shaped frame. The upper ends of arms 48, 49 are fastened to a metal ring 50 to which the lowermost turn 51 of the spring 14 can be suitably anchored. The uppermost turn 52 abuts against the flange 53 so that the spring 14 tends to urge the ring 50 `and the operating rod 54 downwardly, enabling the spring 14 to assume its normally relaxed state in which all the turns are spaced from each other corresponding to the maximum inductance setting. To reduce the inductance the rod 54 is moved upwardly resulting in a short-circuiting compression of two or more of the lower turns. In Fig. 14 the device is shown in an intermediate adjustment wherein the first four lower turns are thus short-circuited.

If desired, the spring 14 may be arranged to normally close its turns when allowed to return to a relaxed state. Adjustment would then be made by stretching the spring, it being understood however, that when stretched the larger turns would open rst since they are the weakest.

It will be understood that the invention is not limited to any particular number or diameter of the spring turns, or to any particular turn pitch or to any particular taper. If the spring taper qb (Fig. 15) is great enough then when the lower turns are compressed, instead ofassuming a frusto-conical compacted shape, as in Figs. 13 and 14, they may assume a flattened nested shape, as shown in Fig. 16, thus causing those turns to lie dat against the metal ground plate 10. With such an arrangement the lowermost turn 55 need not be anchored to the plate 10, so that it can spread out circumferentially.

Furthermore, the invention is not limited to a spring turning element wherein all the turns are of the same pitch. Thus as schematically shown in Fig. 17, the turns may be of non-uniform pitch. Fig. 18 shows how the lower turns of such a spring tuning element are compacted during the adjustment of their inductance. Furthermore the spring may be mounted in the reverse relation to that shown in Figs. 1 to 18. Thus, as shown in Fig. 19, the spring 14 can be mounted with the apex end of the tapered helix in contact with the ground plate 10 and with the operating arm 11 connected to the opposite largest end turn. Here again the turns of the tapered helix need not be of the same pitch, but may be of non-uniform pitch.

From the foregoing it will be seen that as a load is applied to the tapered helix tuning unit, the turns of largest diameter will deflect most readily and will close first. Further application of load will cause the next adjacent turn to close on the previous closed turns. The resultant action is that, as the turns close upon themselves, a point of contact is generated along the helix beginning from the bottom end, travelling upward.` All turns to one side of this contact point are in resilient pressurized contact with one another, while all turns to the other side of this contact point are in proportional spacing to one another. By varying the applied force to such a device, the said point of contact may be correspondingly varied.

Graph 56 of Fig. 20 shows the relation between force and deflection where the turns of the tapered helical spring unit are of uniform or constant pitch, while graph 57 shows the relation between force and deliection for a tapered helical spring unit with the turns of non-uniform pitch and with wider spacing at the small end, as illustrated in Fig. 17. it is quite clear, therefore, that by choosing the non-uniformity of pitch any desired inductance variation with respect to movement of the operating rod 11, 21, 34 or 54, can be obtained.

Various changes and modilications may be made in the disclosed embodiments without departing from the spirit and scope of the invention.

We claim:

1. A tunable antenna comprising a conductive member, means coupling said conductive member to ground, an adjustable inductance in the form of a multi-turn spring wire helix having one end thereof coupled to said conductive member, and an adjustable operating member passing through said conductive member and connected to the opposite end of the helix to extend and contract said helix with respect to said conductive member, and thereby to tune the antenna to a selected frequency and change the physical length of the antenna above the ground plane and also change thereby the inherent inductance and the inter-turn capacitance of said helix, said adjustable operating member being independent of the electrical relation between said helix and said conductive member.

2. A tunable antenna according to claim 1, in which said inductance is in the form of a tapered multi-turn spring wire helix with the base of the helix abutting against said conductive member.

3. A tunable antenna according to claim 1, wherein said conductive member comprises a radiator sleeve and coupling means therefor adjacent the base end thereof.

4. An antenna tuning unit comprising an enclosing conductive housing having slidably mounted therein a conductive plate, means coupling said conductive plate to said housing, means coupling said housing to ground, an adjustable inductance comprising a multi-turn tapered helical coil of spring wire, the base of said coil being in contact with said plate, an adjusting member extending through one end of said housing and connected to said plate, a lead-in insulatingly anchored through the housing wall, and means anchoring the apex end of said coil to said lead-in, the turns of said inductance being in uncompacted spaced relation when in one extreme state of adjustment and in compacted short circuiting relation when in the opposite extreme state of adjustment.

5. An antenna tuning unit comprising and adjustable inductance in the form of a tapered multi-turn spring wire helix, the turns of which are spaced when the helix is in the relaxed state, an insulator form nested Within said helix and having a taper which conforms to the normal taper of said helix and against which the helix turns are held by their own springiness, said form having a helical multi-turn shoulder to engage the turns of the helix to stabilize them against Vibration, means coupling the base of said helix to a ground plane, and adjusting means to compact the helix to cause the larger diameter turns to be progressively moved into compacting, contacting relation and thereby to vary the inductance of the'unit and change the physical length of the helix above the ground plane and also change thereby the inherent inductance and inter-turn capacitance of said helix.

6. An antenna unit according to claim 5, in which said form is carried by said adjusting means, the apex of the form being connected to the apex of said helix.

7. An antenna unit according to claim 5,'in which said form is stationarily mounted and the base end of said helix is attached to a support forming part of the helixy adjusting means.

8. A tunable antenna comprising a conductive merri-V in the form of a multi-turn spring wire helix having the r` base end thereof coupled to said conductive plate, an adjustable operating member passing through said radiator and said plate and connected to the apex end of said helix to extend and contract said helix with respect to said radiator and thereby tune the antenna to a selected frequency and change the physical length of said antenna above said conductive plate, and also change thereby the inherent inductance and inter-turn capacitance of said helix, and coupling means for said antenna adjacent the base end of said radiator.

9. An antenna tuning unit comprising an enclosingv normal taper of said helix, said taper including a continuous helical shoulder and against which the helix turns are held by their own springiness, adjusting means coupled to said form to compactthe helix to cause the larger diameter turns to be progressively moved into compacting. contacting relation and thereby vary the inductance ofthe unit and change the physical length of the antenna above the ground and also change thereby the inherent inductance and inter-turn capacitance of said helix.

10. An antenna tuning unit comprising an enclosing conductive housing having slideably mounted therein a conductive annular plate and electrically coupling said plate to said housing, an adjustable inductance-in the form of a tapered multi-turn helix the turns of which are spaced when the helix is in a relaxed state,'the base of said helix being in contact with said plate, means coupling said plate to housing, a lead-in insulating passing through the housing wall, means anchoring the apex end of said coil to said lead-in, an insulator form nested within said helix and having a taper which conforms to the normal taper of said helix said taper including a continuous helical shoulder and against which the helix turns are held by their own springiness, said form being stationarily mounted to said housingand adjusting means coupled to said plate to compact the helix to cause the larger diameter turnsto be progressively moved into compacting kcontacting relation and thereby vary the inductance of the unit and change the physical length of the antenna above ground and also change thereby the inherent inductance and inter-turn capacitance of said helix.

References Cited in the tile of this patent UNITED STATES PATENTS 488,121 Houghton et al. Dec. 13, 1892 41,036,304 Misland Aug. 20, 1912 1,232,450 Misland July 3, 1917 2,252,919 Eckard v Aug. 19, 1941 2,294,881 Alford Sept. 8, 1942 2,498,350 Walsh Feb. 21, 1950 ,2,563,413 Ostrow Aug. 7, 1951 2,566,761 Dubilier Sept. 4, 1951 2,629,013 Gluyas Feb. 17, 1953 FOREIGN PATENTS 430,548 Great Britain June 20, 1935 909,583 Germany Apr. 22, 1954 

